The use of secondary ion mass spectrometry for investigating oxygen in pyrometallurgical reactions

The investigation of oxygen concentration gradients in iron samples by using the dynamic secondary ion mass spectrometry (SIMS) technique was presented. Meta droplet were prepared by melting iron and aluminum pieces in a small electric arc furnace in an argon atmosphere during the investigation. The results showed that the oxygen behavior during the reaction between metal and slag was more complex

Analysis of the source of dynamic interfacial phenomena during reaction between metal droplets and slag

The dynamic interfacial phenomena during high-temperature reaction between an Fe-Al alloy droplet and a CaO-SiO2-Al2O3 slag were analyzed by evaluating the thermocapillary, solutocapillary, and electrocapillary effects. The magnitudes of these effects were determined using the local equilibrium model and utilizing kinetic data to determine local composition, temperature, and electrical potential. The electrocapillary effect was found to be dominant. It contributed approximately 85 pct of the maximum interfacial depression while the solutocapillarity contributed 15 pct. The thermocapillary effect was found to be negligible. In this work, the local gradient of interfacial tension along the interface due to the solutocapillary effect was estimated, i.e., Delta(gamma m-s) to 440 mN/m over a 1- to 2-mu m distance

Analysis of interfacial area changes during spontaneous emulsification of metal droplets in slag

In some metal/slag reactions involving spontaneous emulsification, there is a significant increase of interfacial area, which in turn affects the global rate. In previous work by the authors, the reaction between Fe-Al alloy droplets and CaO-SiO2-Al2O3 slag was investigated. Re-evaluation of the data has shown that at an initial reaction rate above 9 x 10(-7) mol min(-1) mm(-2), the maximum change in interfacial area increases linearly with the initial rate and with the change of free energy due to chemical reaction. There were found to be two sources of interfacial area increase: (a) flattening of the original droplet, which was independent of initial rate; and (b) separation of smaller droplets, which was dependent on the initial rate

Kinetics of metal/slag reactions during spontaneous emulsification

An approach for accommodating the interfacial area changes in kinetic equations for heterogeneous reactions in the presence of spontaneous emulsification has been proposed. The kinetics were analyzed by incorporating time-averaged interfacial areas in the rate equations. The approach was found to be applicable for the experimental data and to satisfactorily describe the reaction kinetics. In the case of a high-temperature reaction between 2.35 g Fe-5 wt pct Al alloy metal droplets with CaO-SiO2-Al2O3 slag at 1650 degrees C, it was found that the kinetics follow a first-order relationship with respect to aluminum in the metal, and it was concluded that they were controlled by mass transport in the metal phase. The calculated metal mass-transfer coefficient k(m) was 1.7 x 10(-6) m/s

A thermodynamic-based life cycle assessment of precious metal recycling out of waste printed circuit board through secondary copper smelting

© 2017 Elsevier B.V. This study provides an environmental impact assessment of the black copper smelting route for the processing and recovery of copper and other valuable metals such as gold and silver from waste printed circuit boards (PCB). Thermodynamic based analysis was conducted to simulate the recycling process and a life cycle assessment was carried out to estimate and compare the environmental impact of the two scenarios: (1) recycling of precious metal out of waste PCBs through secondary copper smelting (Electronic Waste Processing, EWP); and (2) secondary copper recycling without adding electronic waste to the feed (SCR). The results of the study revealed that environmental impacts of using e-waste along with low-grade copper scrap in existing smelters to recover precious metals are dependent on the distance the material feed travels to the smelter and the means of electricity supplying the smelter. It is also found that the impact of the EWP scenario for climate change, freshwater eutrophication, and fossil depletion is significantly higher than those obtained from the SCR scenario and it is mainly because the metal and oxide dust in former scenario needs to be further refined to recover metals such as nickel, zinc and lead. The results also confirm that 10% cut in electricity usage in EWP scenario, has the higher environmental benefit in almost all dominant categories

Thermodynamic analysis of metals recycling out of waste printed circuit board through secondary copper smelting

© 2017, Springer Japan. In this paper, a detailed thermodynamic analysis of processing of electronic waste (e-waste), particularly printed circuit boards (PCB), through secondary copper recycling (black copper smelting), was carried out. The mass balance flowsheets of two scenarios, i.e., the case of secondary copper recycling with (SCE1) and without (SCE2) addition of PCBs, have been developed and compared. From the perspective of recovery of copper (Cu), gold (Au), and silver (Ag); the thermodynamic analysis predicted that the process conditions at temperature of 1300 °C and oxygen partial pressure (pO2) of 10–8 atm are suitable for PCB processing through secondary copper smelting route. Under these conditions, no solid phases were predicted to form when the PCB addition is below 50 wt%. High PCB addition was predicted to produce high volume of slag in the process and more pollutants in the gas phase (Br-based gaseous compounds). The chemistry of the slag was also predicted to change that is shifting the liquidus temperature to a higher value due to the presence of aluminium (Al), silica (SiO2), and titanium dioxide (TiO2) in the feed coming from the PCB. The carbon content of the PCB potentially supplies additional heat and reductant (CO) in the process hence can partially replace coke in the feed material. The predicted recoveries of copper (Cu), gold (Au), and silver (Ag) from e-waste were 83.3, 96.5, and 88.5 wt% respectively

Understanding of Bath Surface Wave in Bottom Blown Copper Smelting Furnace

The waves formed on bath surface play an important role in the bottom blown copper smelting furnace operations. Simulation experiments have been carried out on model of the bottom blown furnace to investigate features of the waves formed on bath surface. It was found that the ripples, the 1st asymmetric standing wave and the 1st symmetric standing wave were able to occur in this model, and empirical occurrence boundaries have been determined. The amplitude and frequency of the standing waves have been systematically investigated. It was found that the amplitude of the 1st asymmetric standing wave is much greater than the 1st symmetric standing wave and the ripples; and the amplitude is found to increase with increasing bath height and flowrate but decrease with blowing angle. The frequency of the 1st asymmetric standing wave is found increasing with bath height but independent of flowrate and blowing angle

High Temperature Processing Symposium

This presentation will report the processing of e-waste and extraction of the valuable metals through secondary copper smelting route (black copper smelting), as shown in Figure 1. The rationale for choosing the selected route will be explained. The approach taken in the study includes combined thermodynamic and process flowsheet modelling followed by economic as well as environmental impact assessments. The results of the study confirm the need for further study on the behaviour of various elements for the modelling for improvement of the process. The result from the economic study also showed that the selected process route is economically viable. The largest impact was found to be from the variation of the raw material cost, followed by the interest rate on borrowing capital. It was found that the minimum plant capacity for the process to be still economically viable is predicted to be 30,000 tonnes/annum

Understanding of bath surface waves in bottom blown copper smelting furnace

In recent years, a bottom blown copper melting technology has been developed by Fangyuan Nonferrous Metals in China. The main unit of the technology is a bottom blown smelting furnace with a dimension of 4.4m in diameter and 16.5m in length. At the bottom of the furnace, there are nine lances aligned in two staggered rows, five in the upper row, 22º offset from vertical line, and four in the lower row 7º offset from vertical line. During smelting, oxygen enriched air is blown into molten bath from bottom lances and leads to different types of standing waves on bath surface. The features of the different standing waves are highly associated with bath splash, and can have an effect on refractory abrasion, matte droplet entrainment and settlement, and viscous slag tapping. This study aims to identify the types of standing waves that could occur in bottom blown furnace, summarise conditions of occurrence and analyse their amplitude and frequency to assist industrial operation